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- Question
A broadside array operating at 100 cm wavelength consist of 4 half-wave dipoles spaced 50 cm apart. Each element carries radio frequency current in the same phase and of magnitude 0.5 A. The radiated power will be
Options- A. 196 W
- B. 73 W
- C. 36.5 W
- D. 18.25 W
- Correct Answer
- 196 W
ExplanationP = n . I2 . Rr, where Rr = 80p2
?.
n = 4.
More questions
- 1. Noise generated in a resistor is also known as
Options- A. partition noise
- B. white noise
- C. thermal noise
- D. shot noise Discuss
Correct Answer: thermal noise
- 2. A reactor is used in a dual converter operating in non-circulating current mode.
Options- A. True
- B. False Discuss
Correct Answer: False
Explanation:
Reactor is used only for circulating current mode.- 3. The colour code on a carbon resistor is red-red-black-silver. The value of resistor is
Options- A. 22000 ?
- B. 2200 ?
- C. 22 ± 5% ?
- D. 22 ± 10% ? Discuss
Correct Answer: 22 ± 10% ?
- 4. A piece of copper and another piece of Germanium are cooled from 30°C to 80 K. The resistance of
Options- A. copper decreases and germanium increases
- B. both decreases
- C. both increases
- D. copper increases and germanium decreases Discuss
Correct Answer: copper decreases and germanium increases
Explanation:
As temperature is decreased, resistance of conductors decreases and resistance of semiconductors increases.- 5. When a dielectric is subjected to an electric field E, each volume element of dielectric can be considered to be carrying an electric dipole moment.
Options- A. True
- B. False Discuss
Correct Answer: True
- 6. As regards ?0 and ?r (absolute and relative permittivity)
Options- A. both ?0 and ?r can be interpreted in terms of atomic properties of medium
- B. only ?r can be interpreted in terms of atomic properties of medium
- C. only ?0 can be interpreted in terms of atomic properties
- D. ?r has no physical significance Discuss
Correct Answer: only ?r can be interpreted in terms of atomic properties of medium
- 7. At a very low temperature, a semiconductor
Options- A. becomes a conductor
- B. becomes an insulator
- C. may become a conductor or an insulator
- D. will remain a semiconductor becomes a conductor or an insulator Discuss
Correct Answer: becomes an insulator
Explanation:
Semi conductor becomes insulator at very low temperature.- 8. As per Bohr's postulate, only those circular orbits are stable for which the angular momentum is equal to an integer times
.
Options- A. True
- B. False Discuss
Correct Answer: True
Explanation:
It is a quantum condition postulated by Bohr.- 9. In a specimen of silicon steel, a field strength of 200 A/m causes a flux density of 0.5 T. In a specimen of cast iron, the same H would cause B to be
Options- A. 0.5 T
- B. less than 0.5 T
- C. more than 0.5 T
- D. 0.5 T or more or less Discuss
Correct Answer: less than 0.5 T
Explanation:
Because cast iron has lower permeability than silicon steel.- 10. Transformer oil is
Options- A. refined vegetable oil
- B. refined mineral oil
- C. mixture of vegetable and mineral oil
- D. none of the above Discuss
Correct Answer: refined mineral oil
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